If you are being asked to go deeper (beyond basic codes), rather than reinventing the wheel, you could try using ARTG* codes.

See this site ... try searching for electrocardiograph for example. Note that you can save (export) search results to .xls.

Meanwhile, how about yet another code-base ... take a look at UNSPSC** ... and try entering electrocardiograph in the Code Name field.

* Australian Register of Therapeutic Goods
** United Nations Standard Products and Services Code

Note that UNSPSC is associated with GS1 (formerly the Uniform Code Council) - another one that has become popular. Yes; there's money in codes!

But UNSPSC is not too bad, as (at least) it uses an hierarchical (8-digit) structure.

If you don't inspect ... don't expect.